A jaw crusher, which crushes raw materials by moving a swing jaw close to and away from a stationary jaw, has been conventionally known (for example, Japanese Patent Publication No. 5-45300, especially, pages 1 to 3, and FIG. 1 and FIG. 2). In this jaw crusher, the grain size of a crushed product is determined by an outlet clearance between lower ends of the stationary jaw and the swing jaw, and an outlet clearance adjustment mechanism is provided so as to make the outlet clearance adjustable. The outlet clearance adjustment mechanism includes a toggle plate of which one end is made abut to the swing jaw, and a toggle block to which the other end of the toggle plate is made abut, and the outlet clearance adjustment mechanism is constituted by constituting the toggle block in a link shape and rotatably supporting it. When the toggle block is rotated, the swing jaw is moved close to and away from the fixed jaw via the toggle plate, and the outlet clearance between the lower ends of the swing jaw and the stationary jaw can be adjusted. In this outlet clearance adjustment mechanism, an angular sensor or the like is provided at a rotary shaft of the toggle block so that the outlet clearance can be detected according to an amount of rotation of the toggle block.
However, the outlet clearance adjustment mechanism including the toggle block usually also plays the role of a reaction force receiving mechanism which receives a reaction force from the swing jaw which is crushing. Consequently, the angle sensor, which is mounted to the toggle block, causes the problem that the angle sensor is vibrated by a reaction force which is repeatedly exerted on the toggle plate and the toggle block from the swing jaw, an impact at the time of crushing and the like, and thus it cannot detect the angle with stability. In addition, there exists the problem that a sensor with high resolution is expensive.